Living in the clouds

Despite suffering from acute motion sickness, meteorologist and explorer Felicity Aston found that travelling by airship across the USA from the Atlantic to the Pacific coasts offered a unique opportunity to study the mechanisms at work in the atmosphere

My first surprise came during take-off. I had imagined that the airship would rise slowly from the ground like a hot air balloon. It felt more like the launch of a rocket. The nose lifted towards the sky and I was tilted back into my seat as if I was heading to the Moon.

As we powered upwards, the horizon outside slanted at an alarmingly steep angle. But the view was spectacular. Windows lined our long, narrow gondola and the panes had been removed for ventilation, which made it possible to lean out and into the draft. The effect was a near-total panorama of landscape and sky.

We moved more slowly than a conventional aeroplane so there was time to take in all of the details on the ground. The experience was utterly absorbing. The difference between flying in a small aircraft and flying in this airship was akin to the difference between driving and cycling – it felt as though we were travelling through the scenery rather than sliding over it.

The way that the airship moved in flight was my second big surprise. Initially, it seemed remarkably steady, but over time, the motion became strangely undulating, with occasional steep climbs as the tip of the gas-filled envelope was forced upwards by a rising thermal, followed by an equally dramatic nose-dive as the pilots quickly corrected the ascent.

I learnt that the resulting nose-to-tail listing is called ‘dolphining’ because the motion is a bit like a dolphin leaping through the waves, but my stomach decided that it was more like the nauseating list of a freighter in a heavy sea. I suffer from horrible motion sickness on ships and I found that an ‘air ship’ is no exception. The movement took some getting used to.

SCIENTIFIC GOAL

I was on board the airship for a month-long expedition across the USA from Florida’s Atlantic coast to San Francisco on the Pacific coast. Most of the 13 passenger seats inside the gondola had been removed to make way for the scientific instruments that we would need in order to make a study of the science of the skies. For this reason, our airship was re-named Cloud Lab.

As the meteorologist on the Cloud Lab team, my task was to look at the atmosphere, the clouds and the weather. I worked alongside atmospheric chemist Dr Jim McQuaid. Also on board were entomologist Dr Sarah Beynon and our tropical and infectious diseases specialist Dr Chris van Tulleken, both of whom looked at life in the clouds.

We were able to ask the pilots to direct the airship more or less as we pleased so that we could get the most out of our on-board experiments. There wasn’t enough room for everyone to sleep in the gondola, so each evening, the airship would return to Earth.

Landing an airship is even more extraordinary than taking off. It all boils down to the weight of your ground crew.

Cloud Lab was accompanied by a ground crew of 14 men and a mobile mast mounted on the back of a lorry. As the airship approached the airfield, the crew would arrange themselves into a V-formation.

When the airship was sufficiently close to the ground, six members of the crew grabbed hold of two tow ropes that trailed from the nose of the helium-filled envelope and pulled the airship out of the sky. The rest of the team raced to lay hands on the gondola itself, holding it on the ground with their combined body weight until the nose of the airship was safely attached to the top of the lorry’s mast.

After we disembarked, the airship was left to swing freely around the mast during the night. In strong winds, it was prone to lift off the ground completely in a motion called ‘kiting’. The crew nonchalantly recalled the airship rising to an almost 90° angle on one particularly stormy night. Fortunately, no-one was on board at the time.

ENVELOPE MECHANICS

There was something special about being able to return to our airstrip each morning, spotting the glorious torpedo-shaped airship towering above all the other parked aircraft, and being able to say, ‘That one’s ours!’ Cloud Lab was a Skyship 600, one of the largest commercial airships flying today. The 12-metre gondola is dwarfed by the nearly 60-metre envelope that bulges above it to a height of 20 metres.

The Skyship 600 is known as a ‘non-rigid’ airship because there’s no frame inside the envelope. Instead, the envelope is maintained through a combination of its design characteristics and the low pressure of its internal gas.

The envelope contains more than 6,000 cubic metres of gas, not all of it helium. Two air-filled bags called ‘ballonets’ sit inside the envelope. The buoyancy of the airship is controlled by expelling air from the ballonets to help conserve the more expensive helium, which is only vented when absolutely necessary.

Two Porsche engines are mounted on helicopter propellers towards the aft of the gondola. They can be rotated from horizontal to vertical and look for all the world like oversized office fans. This propulsion system gives the airship its extraordinary take-off ability, as well as an impressive top speed of 56 knots.

The engines use aviation fuel and consume just eight gallons per hour when cruising at 30 knots. Compare this to a 12-seater twin-turbine aircraft, which typically consumes ten times as much fuel as the Skyship 600 but which cruises only eight times faster.

WEIGHING A CUMULUS

Cloud Lab’s unique attribute as an expedition vehicle was its ability to move through the air at relatively slow speeds. This gave us an opportunity to get a detailed insight into the processes at work around us.

Clouds are so familiar that it’s generally assumed that we already know everything about them. In fact, the journey had barely started before our view of the skies was being challenged.

One of our first experiments was to look at how much water is in the average cumulus cloud. We wanted to know if it was possible to weigh a cloud.

To find out, we had to go cloud hunting. This sounds simple enough. The skies over the Gulf Coast are full of convective cumulus that bubble up in the tropical heat. However, clouds aren’t stationary objects – they’re constantly developing and dissipating, with a lifespan of only about ten minutes. All of which makes a cumulus difficult to catch in a slow-moving airship.

Eventually, we flew directly through a distinct cumulus cloud. By timing our passage through the cloud, we were able to calculate its volume. Combining these data with measurements of water-droplet density (gathered by a probe) allowed us to determine the approximate weight of the cloud.

The result proved to be a surprise. We tend to think of clouds as being light and fluffy, so it was a shock to discover that our skies are loaded with objects that are as heavy as an elephant.

CLOUD BIODIVERSITY

The search for life in the clouds was equally surprising. During each flight, an insect net was deployed out of a window. It was inspected at regular intervals to see which species exist at different altitudes.

More intriguing still were the data from a waveband integrated bio-aerosol sensor (WIBS) installed on the airship. The WIBS can detect and classify miniscule particles in the air (using UV-excited fluorescence) to identify pollution, pollen, fungal spores and bacteria. While waiting for the results from the WIBS, we realised that if bacteria were detected, we would need to investigate the role that clouds play in the transfer of bacteria from place to place.

As we voyaged westwards from the tropical humidity of the Gulf Coast towards the dry western states of New Mexico and Arizona, the meteorology and the landscape around us changed, along with the science.

In the desert environment, hunting clouds was a lot more difficult. Arizona is hot and arid, so any clouds that form do so at an extremely high altitude. They are also very thin. To detect them, we had to use light detection and ranging, more commonly known as ‘light radar’. We used a green laser to detect clouds over a range of 15 kilometres, and analysed what they were made of by distinguishing between ice particles and water droplets.

After a fascinating month of flying, Cloud Lab finally arrived at the Pacific coast. Our airship had given us an unprecedented insight into the atmospheric mechanisms at work in the sky.

Along the way, we had discovered that travel by airship is neither reliable nor practical: our route and schedule were frequently affected by weather, altitude and landscape. Nevertheless, for a detailed exploration of the skies and a glimpse into our planet’s weather from inside its weather-making machines, there’s no better vehicle.

History’s most famous airship, the Hindenburg, burst into flames on 6 May 1937 as it came in to land at a New Jersey airfield after a routine transatlantic flight. The explosion killed 36 people.

The disaster happened because the rigid-framed Zeppelin was filled with hydrogen, which is a highly flammable gas. Cloud Lab, like all other modern airships, uses helium because it doesn’t burn.

The ubiquity of helium-filled party balloons belies the fact that the gas is extremely rare. It’s formed by natural radioactive decay and extracted from natural gas, and there are concerns over its conservation and use.

Since the early 1900s, the USA has been the world’s only significant source of helium, thanks to a concentration located beneath the Great Plains. In 1925, a National Helium Reserve was established to stockpile the gas. The resource has been managed so well that today it still accounts for more than a third of the world’s helium. However, the supply is now running out. Fears of a shortage have inflated the price of helium and have prompted a search for new reserves.

Ironically, the Hindenburg was designed to use helium, but when the USA refused to sell any of the gas to its owner, the design was altered to make use of hydrogen. And as we now know, this decision brought the age of the airship to a disastrous end.

ESSENTIAL GEAR

Ear plugs, a weather meter and a supply of motion sickness treatment are among the list of unusual equipment that Felicity Aston took with her on her month-long expedition across the skies above the USA. And although she was airborne for the majority of the trip, a good pair of shoes also proved vital

1. Ear protection

Ear Peace High Definition Ear Plugs

£15/8.5 grams

These ear plugs cut out background noise and help to protect your ears from excessive sound while permitting clear hearing – perfect for use on an airship

2. Binoculars

Nikon Standard Action EX Series 8x40 CF

£125/855 grams

Binoculars are essential on an airship for a closer inspection of the scenery and wildlife beneath. These high-performance, fog-free and waterproof binoculars are at the affordable end of the binocular budget scale

3. Weather app

Foreflight

US$75 per year

An innovative app for iOS devices that overlays weather data onto air charts in near real time. This powerful tool provides an easy visualisation of current weather conditions for 220 countries

4. Red-light torch

Energizer 6 LED Headlight

£13.50/91 grams (with batteries)

White lights inside the airship must be turned off during night flights to ensure that the pilots aren’t dazzled. One of our cameramen had the foresight to bring this inexpensive LED head torch. The red light option enabled him to continue working while the airship was airborne

5. Handheld weather meter

Kestrel 2500

£135/65 grams

This pocket-sized sensor can detect a raft of weather data, from wind speed and temperature to pressure trends and altitude. Although it isn’t calibrated, it’s useful on the ground to determine the likelihood of flying weather, and useful in the air to establish rough altitude

6. Book

The Cloudspotter’s Guide

£8/410 grams

Written by the chairman and founder of the Cloud Appreciation Society, this book offers a complete introduction to clouds and their cultural history

7. Camera

GoPro Hero3 White Edition

£200/74 grams

The Wi-Fi function on this camera enables the device to be controlled remotely. This feature allowed our production team to fix multiple GoPros to the outside of Cloud Lab to film take-offs and landings. The resulting footage could be viewed instantly via the GoPro app – sold separately for various mobile devices

8. Nausea relief

Transderm Scop

Standard prescription charges/2 grams

These small, circular patches are worn behind the ear and are effective for up to three days. They deliver small doses of the drug Scopolamine and are available only with a prescription from your doctor. There can be side effects, so they’re not suitable for everyone

9. Two-way radio

Hytera TC-320 446

from £49/146 grams (with antenna and battery)

This licence-free analogue radio has a lithium-ion battery that delivers up to ten hours of performance on a single charge and can be charged and programmed via a mini USB interface

10. Footwear

Ecco Xpedition II Ladies

£115/1.1 kilograms

Airships often land on scrubland at the edge of small airfields, where snakes, biting insects and cutting grasses abound, so robust footwear is essential. A gripping sole was useful on board the Skyship 600, and these waterproof and breathable shoes meet both criteria

This story was published in the June 2014 edition of Geographical Magazine

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